1. Field of the Invention
The present invention relates, generally, to a signal transmission device and method and, more particularly, to signal transmission where, in case of transmitting signals through a transmission line which is configured of a number of high-speed serial buses and a low-speed serial bus having a transmission speed lower than that of the high-speed serial buses, the operation of signal transmission through the number of high-speed serial buses is controlled on the basis of the result of communications through the low-speed serial bus.
2. Description of the Prior Art
It has been common practice that a computer device or the like converts a digital picture signal into an analog picture signal which is fed to a display device by analog transmission. However, with the spread of a display device in which a display unit is driven using a digital signal, such as a liquid crystal display, for example, a method in which a picture signal is transmitted as a digital signal has been standardized for the purposes of preventing the degradation of a picture quality, the curtailment of (a cost, etc. By way of example, DVI (Digital Visual Interface, Version 1.0) standards have been stipulated by the DDWG (Digital Display Working Group). According to the DVI standards, a digital picture signal is transmitted using a TMDS (Transition Minimized Differential Signals) link developed by Silicon Image, Inc. in the U.S. The interface is provided data transmission lines for the respective channels of red, green and blue and a clock transmission line of one channel, and the picture signals of the respective channels of red, green and blue are transmitted with a baseband. In addition, the interface includes an I2C bus being a bidirectional serial transmission line which has a transmission speed lower than that of the high-speed serial buses of the TMDS link. The I2C bus is employed as a transmission line for DDC (Display Data Channel) standards for a plug-and-play function as stipulated by the VESA (Video Electronics Standards Association).
Meanwhile, the connection scheme of the DVI standards is such that transmission equipment such as a computer device, and reception equipment such as a display device, are connected in point-to-point fashion. Thus, the picture signals of the respective channels of red, green and blue are digitally transmitted unidirectionally from the transmission equipment to the reception equipment and at high speed with the baseband by the use of the TMDS link. Herein, an audio signal, a data signal, etc. cannot be transmitted at high speed. Besides, owing to the plug-and-play function, it is set whether the digital picture signal is to be transmitted using the data transmission lines of the six channels of the TMDS channel or to be transmitted using the data transmission lines of the three channels thereof. Herein, when the transmission of the digital picture signal is set so as to use the data transmission lines of the three channels, the data transmission lines of the remaining three channels fall into reserved states, wherein the data transmission lines are not effectively utilized. Further, the respective picture signals of red, green and blue are transmitted in conformity with GTF (Generalized Timing Formula) stipulated by the VESA. Herein, since a blanking period is held in the GTF standards, transmission efficiency is not yet sufficiently high even in the transmission of the digital signal.